An interesting — and potentially illuminating — contrast has developed within the Republican Party about its previous enthusiastic support for the foreign interventions favored (especially after 9/11) by former President George W. Bush and especially his vice president, Dick Cheney, and an emerging embrace of limited overseas engagement.

The contrast has been perhaps most evident in the differences between outspoken freshman Sen. Rand Paul (and those, like the tea party, who agree with him) and those Republicans who still believe our country must continue to play a dominant role in global affairs.

One of the important corollary arguments, inevitably, is how much money the American taxpayers should pay in taxes to support the Pentagon, so the debate within the GOP has important implications for the federal budget and for our country’s fiscal and tax policies as a whole.

“A real challenge for the Republicans as they approach 2016 is what will be their brand?” commented Richard N. Haass, the president of the Council on Foreign Relations and a former aide to the first President Bush. “The reason Rand Paul is gaining traction is overreaching in Iraq. What he is articulating represents an alternative to both.”

This week is especially important for Republicans because the Conservative Political Action Conference (CPAC) is being held — and closely observed by everyone interested in American politics — near Washington, D.C. It is with the 2016 presidential election in mind that the country’s most outspoken conservatives have gathered to hammer out something similar to a platform with which to compete for the White House.

Upon convening, it became immediately apparent that there are deep differences among the delegates. At the Thursday opening session Sen. Marco Rubio, the Florida Republican who many (including the tea party) consider a likely candidate for the presidential nomination in 2016, worried about a return to isolationism, as reflected by Sen. Paul’s public speeches, although he never mentioned Paul by name.

While Rubio conceded that the United States “can’t solve every war” he added that “we also can’t be retreating from the world.”

It didn’t take long for Paul to respond. He told the conference that the 13-hour filibuster he conducted last week to protest the Obama administration’s drone policy was actually aimed at identifying the limits on presidential power and American power abroad.

“No one person gets to decide the law,” he said.

But Paul’s sudden surge to national prominence is worrying some of his party’s faithful. They are so opposed to the positions he and his supporters are so eagerly pushing that they have begun talking among themselves about how to thwart Paul and the tea party in the next round of primary challenges.

Dan Senor, who was part of President Bush’s foreign policy apparatus, said the Paul-led drive to embrace a “neo-isolationist” foreign policy “is sparking discussions among conservative donors, activists and policy wonks about creating a political network to support internationalist Republicans.”

Meanwhile, Paul and the tea party are engaged in a war of words with such fellow Republicans as Sen. John McCain of Arizona, the party’s strongest advocate of an aggressive foreign policy. McCain went so far recently as to describe Paul and his followers as “wacko birds.”

Others may be amused by all this noise coming from the CPAC gathering, but there’s actually a lot at stake. For Rubio to prevail over Rand, or vice versa, is to set the tone of the national political discourse for the next few years.